Gene Summary

Gene:POLK; DNA polymerase kappa
Aliases: DINP, POLQ, DINB1
Summary:This gene encodes a member of the DNA polymerase type-Y family of proteins. The encoded protein is a specialized DNA polymerase that catalyzes translesion DNA synthesis, which allows DNA replication in the presence of DNA lesions. Human cell lines lacking a functional copy of this gene exhibit impaired genome integrity and enhanced susceptibility to oxidative damage. Mutations in this gene that impair enzyme activity may be associated with prostate cancer in human patients. [provided by RefSeq, Sep 2016]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:DNA polymerase kappa
Source:NCBIAccessed: 01 September, 2019


What does this gene/protein do?
Show (7)
Pathways:What pathways are this gene/protein implicaed in?
Show (1)

Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 01 September 2019 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

Tag cloud generated 01 September, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (8)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: POLK (cancer-related)

Jiraskova K, Hughes DJ, Brezina S, et al.
Functional Polymorphisms in DNA Repair Genes Are Associated with Sporadic Colorectal Cancer Susceptibility and Clinical Outcome.
Int J Mol Sci. 2018; 20(1) [PubMed] Free Access to Full Article Related Publications
DNA repair processes are involved in both the onset and treatment efficacy of colorectal cancer (CRC). A change of a single nucleotide causing an amino acid substitution in the corresponding protein may alter the efficiency of DNA repair, thus modifying the CRC susceptibility and clinical outcome. We performed a candidate gene approach in order to analyze the association of non-synonymous single nucleotide polymorphisms (nsSNPs) in the genes covering the main DNA repair pathways with CRC risk and clinical outcome modifications. Our candidate polymorphisms were selected according to the foremost genomic and functional prediction databases. Sixteen nsSNPs in 12 DNA repair genes were evaluated in cohorts from the Czech Republic and Austria. Apart from the tumor-node-metastasis (TNM) stage, which occurred as the main prognostic factor in all of the performed analyses, we observed several significant associations of different nsSNPs with survival and clinical outcomes in both cohorts. However, only some of the genes (

Hong KH, Song S, Shin W, et al.
A case of interdigitating dendritic cell sarcoma studied by whole-exome sequencing.
Genes Genomics. 2018; 40(12):1279-1285 [PubMed] Related Publications
Interdigitating dendritic cell sarcoma (IDCS) is an aggressive neoplasm and is an extremely rare disease, with a challenging diagnosis. Etiology of IDCS is also unknown and most studies with only case reports. In our case, immunohistochemistry showed that the tumor cells were positive for S100, CD45, and CD68, but negative for CD1a and CD21. This study aimed to investigate the causative factors of IDCS by sequencing the protein-coding regions of IDCS. We performed whole-exome sequencing with genomic DNA from blood and sarcoma tissue of the IDCS patient using the Illumina Hiseq 2500 platform. After that, we conducted Sanger sequencing for validation of sarcoma-specific variants and gene ontology analysis using DAVID bioinformatics resources. Through comparing sequencing data of sarcoma with normal blood, we obtained 15 nonsynonymous single nucleotide polymorphisms (SNPs) as sarcoma-specific variants. Although the 15 SNPs were not validated by Sanger sequencing due to tumor heterogeneity and low sensitivity of Sanger sequencing, we examined the function of the genes in which each SNP is located. Based on previous studies and gene ontology database, we found that POLQ encoding DNA polymerase theta enzyme and FNIP1 encoding tumor suppressor folliculin-interacting protein might have contributed to the IDCS. Our study provides potential causative genetic factors of IDCS and plays a role in advancing the understanding of IDCS pathogenesis.

Donner I, Katainen R, Kaasinen E, et al.
Candidate susceptibility variants in angioimmunoblastic T-cell lymphoma.
Fam Cancer. 2019; 18(1):113-119 [PubMed] Related Publications
Angioimmunoblastic T-cell lymphoma (AITL) is a subtype of peripheral T-cell lymphoma with a poor prognosis: the 5-year survival rate is approximately 30%. Somatic driver mutations have been found in TET2, IDH2, DNMT3A, RHOA, FYN, PLCG1, and CD28, whereas germline susceptibility to AITL has to our knowledge not been studied. The homogenous Finnish population is well suited for studies on genetic predisposition. Here, we performed an exome-wide rare variant analysis in 23 AITL patients. No germline mutations were found in the driver genes, implying that they are not frequently involved in genetic AITL predisposition. Potentially pathogenic variants present in at least two patients and showing significant (p < 0.01) enrichment in our sample set were found in ten genes: POLK, PRKCB, ZNF676, PRRC2B, PCDHGB6, GNL3L, TTC36, OTOG, OSGEPL1, and RASSF9. The most significantly enriched variants, causing p.Lys469Ter in a splice variant of POLK and p.Pro588His in PRKCB, are intriguing candidates as Polk deficient mice display a spontaneous mutator phenotype, whereas PRKCB was recently shown to be somatically mutated in 33% of another peripheral T-cell lymphoma, adult T-cell lymphoma. If validated, our findings would provide new insight into the pathogenesis of AITL, as well as tools for early detection in susceptible individuals.

Antczak NM, Walker AR, Stern HR, et al.
Characterization of Nine Cancer-Associated Variants in Human DNA Polymerase κ.
Chem Res Toxicol. 2018; 31(8):697-711 [PubMed] Free Access to Full Article Related Publications
Specialized DNA damage-bypass Y-family DNA polymerases contribute to cancer prevention by providing cellular tolerance to DNA damage that can lead to mutations and contribute to cancer progression by increasing genomic instability. Y-family polymerases can also bypass DNA adducts caused by chemotherapy agents. One of the four human Y-family DNA polymerases, DNA polymerase (pol) κ, has been shown to be specific for bypass of minor groove adducts and inhibited by major groove adducts. In addition, mutations in the gene encoding pol κ are associated with different types of cancers as well as with chemotherapy responses. We characterized nine variants of pol κ whose identity was inferred from cancer-associated single nucleotide polymorphisms for polymerization activity on undamaged and damaged DNA, their abilities to extend from mismatched or damaged base pairs at primer termini, and overall stability and dynamics. We find that these pol κ variants generally fall into three categories: similar activity to wild-type (WT) pol κ (L21F, I39T, P169T, F192C, and E292K), more active than WT pol κ (S423R), and less active than pol κ (R219I, R298H, and Y432S). Of these, only pol κ variants R298H and Y432S had markedly reduced thermal stability. Molecular dynamics (MD) simulations with undamaged DNA revealed that the active variant F192C and more active variant S423R with either correct or incorrect incoming nucleotide mimic WT pol κ with the correct incoming nucleotide, whereas the less active variants R219I, R298H, and Y432S with the correct incoming nucleotide mimic WT pol κ with the incorrect incoming nucleotide. Thus, the observations from MD simulations suggest a possible explanation for the observed experimental results that pol κ adopts specific active and inactive conformations that depend on both the protein variant and the identity of the DNA adduct.

Mazzio EA, Lewis CA, Elhag R, Soliman KF
Effects of Sepantronium Bromide (YM-155) on the Whole Transcriptome of MDA-MB-231 Cells: Highlight on Impaired ATR/ATM Fanconi Anemia DNA Damage Response.
Cancer Genomics Proteomics. 2018 Jul-Aug; 15(4):249-264 [PubMed] Free Access to Full Article Related Publications
Sepantronium bromide (YM-155) is believed to elicit apoptosis and mitotic arrest in tumor cells by reducing (BIRC5, survivin) mRNA. In this study, we monitored changes in survivin mRNA and protein after treating MDA-MB-231 cells with YM-155 concurrent with evaluation of whole transcriptomic (WT) mRNA and long intergenic non-coding RNA at 2 time points: 8 h sub-lethal (83 ng/mL) and 20 h at the LC

Li X, Zhao Z, Yi S, et al.
Nuclear Klf4 accumulation is associated with cetuximab drug-resistance and predicts poor prognosis of nasopharyngeal carcinoma.
J Transl Med. 2018; 16(1):183 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The functions of the protein expressed in the nucleus and cytoplasm were different or opposite. The previous study found that oncogene Klf4 played a role of tumor suppressor in the nasopharyngeal cytoplasm. Cetuximab targeted epidermal growth factor receptor (EGFR) for the treatment of nasopharyngeal carcinoma.
METHODS: A cohort of 231 cases of advanced nasopharyngeal carcinoma (7th AJCC III-IVa) samples was assessed by immunohistochemistry (IHC), of which, 63 cases were treated with basic treatment without cetuximab, the basic treatment include chemotherapy and radiotherapy, the regent of the chemotherapy include cisplatin and fluorouracil and 168 cases were treated with cetuximab in addition to the basic treatment. The expression of the KLF4 protein was detected in nucleus and cytoplasm, c-Met protein and nuclear EGFR protein (nEGFR) by IHC, and H-Ras and PI3K mutations by an arms-PCR method in vivo. KLF4 was found to specifically express in the cytoplasm by deleting the NES, while H-Ras and PI3K genes were mutated in the nasopharyngeal carcinoma 5-8F and HONE1cell line. The cetuximab resistance in differentially mutated 5-8F and HONE1 cells was analyzed.
RESULTS: The expression of Klf4 in the nucleus was associated with prognosis in 168 patients with cetuximab-treated nasopharyngeal carcinoma, which was found by retrospective analysis. The KLF4 expression in the nucleus was not significantly correlated with the prognosis in 63 nasopharyngeal carcinoma patients treated with basic treatment (P = 0.261). The expression of Klf4 in the nucleus was correlated with mutations of H-Ras and PI3K in 168 cases of nasopharyngeal carcinoma with cetuximab treatment. In vitro experiments showed that Klf4 was specifically expressed in the nucleus of 5-8F and HONE1 cells as assessed by deleting nuclear export signal, which led to cetuximab resistance. H-Ras and PI3K mutations in 5-8F and HONE1 cells also led to the expression of Klf4 in the nucleus and resistance to cetuximab. In HONE1 cells, Klf4 was specifically localized in the cytoplasm by deleting the NES, and the H-Ras and PI3K mutations did not result in an increased expression of Klf4 in the nucleus and cetuximab resistance.
CONCLUSION: The prognosis of nasopharyngeal carcinoma was not significantly improved by cetuximab treatment when the Klf4 was highly expressed in the nucleus of nasopharyngeal carcinoma tissues. The expression of Klf4 in the nucleus can be used as a biomarker for predicting the effects of cetuximab treatment in nasopharyngeal carcinoma, which might be attributed to the H-RAS and PI3K mutations, leading to cetuximab resistance.

Hamdi Y, Boujemaa M, Ben Rekaya M, et al.
Family specific genetic predisposition to breast cancer: results from Tunisian whole exome sequenced breast cancer cases.
J Transl Med. 2018; 16(1):158 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: A family history of breast cancer has long been thought to indicate the presence of inherited genetic events that predispose to this disease. In North Africa, many specific epidemio-genetic characteristics have been observed in breast cancer families when compared to Western populations. Despite these specificities, the majority of breast cancer genetics studies performed in North Africa remain restricted to the investigation of the BRCA1 and BRCA2 genes. Thus, comprehensive data at a whole exome or whole genome level from local patients are lacking.
METHODS: A whole exome sequencing (WES) of seven breast cancer Tunisian families have been performed using a family-based approach. We focused our analysis on BC-TN-F001 family that included two affected members that have been sequenced using WES. Relevant variants identified in BC-TN-F001 have been confirmed using Sanger sequencing. Then, we conducted an integrative analysis by combining our results with those from other WES studies in order to figure out the genetic transmission model of the newly identified genes. Biological network construction and protein-protein interactions analyses have been performed to decipher the molecular mechanisms likely accounting for the role of these genes in breast cancer risk.
RESULTS: Sequencing, filtering strategies, and validation analysis have been achieved. For BC-TN-F001, no deleterious mutations have been identified on known breast cancer genes. However, 373 heterozygous, exonic and rare variants have been identified on other candidate genes. After applying several filters, 12 relevant high-risk variants have been selected. Our results showed that these variants seem to be inherited in a family specific model. This hypothesis has been confirmed following a thorough analysis of the reported WES studies. Enriched biological process and protein-protein interaction networks resulted in the identification of four novel breast cancer candidate genes namely MMS19, DNAH3, POLK and KATB6.
CONCLUSIONS: In this first WES application on Tunisian breast cancer patients, we highlighted the impact of next generation sequencing technologies in the identification of novel breast cancer candidate genes which may bring new insights into the biological mechanisms of breast carcinogenesis. Our findings showed that the breast cancer predisposition in non-BRCA families may be ethnic and/or family specific.

Long J, Zhu JY, Liu YB, et al.
Helicase POLQ-like (HELQ) as a novel indicator of platinum-based chemoresistance for epithelial ovarian cancer.
Gynecol Oncol. 2018; 149(2):341-349 [PubMed] Related Publications
OBJECTIVE: To investigate the role of HELQ in chemo-resistance of epithelial ovarian carcinoma (EOC), which is a critical factor of patients' prognosis.
METHODS: Immunohistochemistry, survival analysis of our 87 EOC patients and bioinformatics analysis of The Cancer Genome Atlas (TCGA) datasets (Nature, 2011) disclosed the clinical importance of HELQ expression. Quantitative reverse transcription polymerase chain reaction (qRT-PCR), and Western Blot analyses of EOC tissue were used to confirm it. Ectopic overexpression and RNA interference knockdown of HELQ were carried out in OVCAR3 and A2780 cell lines, respectively, to determine the effect of altered HELQ expression on cellular response to cisplatin by CCK8 assay. The DNA repair capacity of these cells was evaluated by using host-cell reactivation assay. Western Blot analyses were carried out to determine the effect of HLEQ on the DNA repair genes by using cells with altered HELQ expression.
RESULTS: HELQ expression associates with response of EOC patients to platinum-based chemotherapy and their overall survival (OS), disease free survival (DFS). HELQ overexpression or knockdown, respectively, increased and decreased the cellular resistance to cisplatin, DNA repair activity, and expression of DNA repair proteins of Nucleotide excision repair (NER) pathway.
CONCLUSIONS: HELQ plays an important role in regulating the expression of DNA repair proteins NER pathway which, in turn, contributes to cellular response to cisplatin and patients' response to platinum-based chemotherapy. Our results demonstrated that HELQ could serve as a novel indicator for chemo-resistance of EOC, which can predict the prognosis of the disease.

Egger ME, Xiao D, Hao H, et al.
Unique Genes in Tumor-Positive Sentinel Lymph Nodes Associated with Nonsentinel Lymph Node Metastases in Melanoma.
Ann Surg Oncol. 2018; 25(5):1296-1303 [PubMed] Related Publications
BACKGROUND: Current risk assessment tools to estimate the risk of nonsentinel lymph node metastases after completion lymphadenectomy for a positive sentinel lymph node (SLN) biopsy in cutaneous melanoma are based on clinical and pathologic factors. We identified a novel genetic signature that can predict non-SLN metastases in patients with cutaneous melanoma staged with a SLN biopsy.
METHODS: RNA was collected for tumor-positive SLNs in patients staged by SLN biopsy for cutaneous melanoma. All patients with a tumor-positive SLN biopsy underwent completion lymphadenectomy. A 1:10 case:control series of positive and negative non-SLN patients was analyzed by microarray and quantitative RT-PCR. Candidate differentially expressed genes were validated in a 1:3 case:control separate cohort of positive and negative non-SLN patients.
RESULTS: The 1:10 case:control discovery set consisted of 7 positive non-SLN cases matched to 70 negative non-SLN controls. The cases and controls were similar with regards to important clinicopathologic factors, such as gender, primary tumor site, age, ulceration, and thickness. Microarray and RT-PCR identified six potential differentially expressed genes for validation. In the 40-patient separate validation set, 10 positive non-SLN patients were matched to 30 negative non-SLN controls based on gender, ulceration, age, and thickness. Five of the six genes were differentially expressed. The five gene panel identified patients at low (7.1%) and high risk (66.7%) for non-SLN metastases.
CONCLUSIONS: A novel, non-SLN gene score based on differential expressed genes in a tumor-positive SLN can identify patients at high and low risk for non-SLN metastases.

Naoum GE, Morkos M, Kim B, Arafat W
Novel targeted therapies and immunotherapy for advanced thyroid cancers.
Mol Cancer. 2018; 17(1):51 [PubMed] Free Access to Full Article Related Publications
Thyroid cancer is a frequently encountered endocrine malignancy. Despite the favorable prognosis of this disease, 15-20% of differentiated thyroid cancer (DTC) cases and most anaplastic types, remain resistant to standard treatment options, including radioactive iodine (RAI). In addition, around 30% of medullary thyroid cancer (MTC) cases show resistance after surgery. The evolving understanding of disease-specific molecular therapeutic targets has led to the approval of two targeted therapies (Sorafenib and Lenvatinib) for RAI refractory DTC and another two drugs (Vandetanib and Cabozantinib) for MTC. These advanced therapies exert their effects by blocking the MAPK pathway, which has been widely correlated to different types of thyroid cancers. While these drugs remain reserved for thyroid cancer patients who failed all treatment options, their ability to improve patients' overall survival remain hindered by their low efficacy and other molecular factors. Among these factors is the tumor's ability to activate parallel proliferative signaling pathways other than the cascades blocked by these drugs, along with overexpression of some tyrosine kinase receptors (TKR). These facts urge the search for novel different treatment strategies for advanced thyroid cases beyond these drugs. Furthermore, the growing knowledge of the dynamic immune system interaction with tumor microenvironment has revolutionized the cancer immune therapy field. In this review, we aim to discuss the molecular escape mechanisms of thyroid tumors from these drugs. We also highlight novel therapeutic options targeting other pathways than MAPK, including PI3K pathway, ALK translocations and HER2/3 receptors and their clinical impact. We also aim to discuss the usage of targeted therapy in restoring thyroid tumor sensitivity to RAI, and finally turn to extensively discuss the role of immunotherapy as a potential alternative treatment option for advanced thyroid diseases.

O'Brien SJ, Carter JV, Burton JF, et al.
The role of the miR-200 family in epithelial-mesenchymal transition in colorectal cancer: a systematic review.
Int J Cancer. 2018; 142(12):2501-2511 [PubMed] Related Publications
Colorectal cancer (CRC) is associated with significant morbidity and mortality as many patients are diagnosed with advanced stage disease. MicroRNAs are small, noncoding RNA molecules that have a major role in gene expression regulation and are dysregulated in CRC. The miR-200 family is involved in epithelial-mesenchymal transition (EMT). This systematic review describes the roles of the miR-200 family in EMT in CRC. A search of electronic databases (PubMed and Embase) was conducted between January 2000 and July 2017. Both in vitro and human studies reporting on the miR-200 family and CRC were included. Studies describing molecular pathways and the role of the miR-200 family in the diagnostic and therapeutic management of CRC were analyzed. Thirty-four studies (22 in vitro and 18 human studies) were included. miR-200 family expression is regulated epigenetically and via transcriptional factor regulation. In vitro studies show that transfection of miR-200 family members into chemo-resistant colon cancer cell lines results in improved chemo-sensitivity and epithelial phenotype restoration. There is intra-tumoral variability in the tissue expression of miR-200 family members with decreased expression at the invasive front. Clinical studies in CRC patients have shown decreased primary tumor tissue expression of miR-429, miR-200a and miR-200c may be associated with worse survival. Conversely, increased blood levels of miR-141, miR-200a and miR-200c may be associated with worse outcomes. The miR-200 family has a central role in EMT. The miR200 family has potential for both prognostic and therapeutic management of CRC.

Ciavarella M, Miccoli S, Prossomariti A, et al.
Somatic APC mosaicism and oligogenic inheritance in genetically unsolved colorectal adenomatous polyposis patients.
Eur J Hum Genet. 2018; 26(3):387-395 [PubMed] Free Access to Full Article Related Publications
Germline variants in the APC gene cause familial adenomatous polyposis. Inherited variants in MutYH, POLE, POLD1, NTHL1, and MSH3 genes and somatic APC mosaicism have been reported as alternative causes of polyposis. However, ~30-50% of cases of polyposis remain genetically unsolved. Thus, the aim of this study was to investigate the genetic causes of unexplained adenomatous polyposis. Eight sporadic cases with >20 adenomatous polyps by 35 years of age or >50 adenomatous polyps by 55 years of age, and no causative germline variants in APC and/or MutYH, were enrolled from a cohort of 56 subjects with adenomatous colorectal polyposis. APC gene mosaicism was investigated on DNA from colonic adenomas by Sanger sequencing or Whole Exome Sequencing (WES). Mosaicism extension to other tissues (peripheral blood, saliva, hair follicles) was evaluated using Sanger sequencing and/or digital PCR. APC second hit was investigated in adenomas from mosaic patients. WES was performed on DNA from peripheral blood to identify additional polyposis candidate variants. We identified APC mosaicism in 50% of patients. In three cases mosaicism was restricted to the colon, while in one it also extended to the duodenum and saliva. One patient without APC mosaicism, carrying an APC in-frame deletion of uncertain significance, was found to harbor rare germline variants in OGG1, POLQ, and EXO1 genes. In conclusion, our restrictive selection criteria improved the detection of mosaic APC patients. In addition, we showed for the first time that an oligogenic inheritance of rare variants might have a cooperative role in sporadic colorectal polyposis onset.

Speltz TE, Danes JM, Stender JD, et al.
A Cell-Permeable Stapled Peptide Inhibitor of the Estrogen Receptor/Coactivator Interaction.
ACS Chem Biol. 2018; 13(3):676-684 [PubMed] Free Access to Full Article Related Publications
We and others have proposed that coactivator binding inhibitors, which block the interaction of estrogen receptor and steroid receptor coactivators, may represent a potential class of new breast cancer therapeutics. The development of coactivator binding inhibitors has been limited, however, because many of the current molecules which are active in in vitro and biochemical assays are not active in cell-based assays. Our goal in this work was to prepare a coactivator binding inhibitor active in cellular models of breast cancer. To accomplish this, we used molecular dynamics simulations to convert a high-affinity stapled peptide with poor cell permeability into R4K1, a cell-penetrating stapled peptide. R4K1 displays high binding affinity for estrogen receptor α, inhibits the formation of estrogen receptor/coactivator complexes, and distributes throughout the cell with a high percentage of nuclear localization. R4K1 represses native gene transcription mediated by estrogen receptor α and inhibits proliferation of estradiol-stimulated MCF-7 cells. Using RNA-Seq, we demonstrate that almost all of the effects of R4K1 on global gene transcription are estrogen-receptor-associated. This chemical probe provides a significant proof-of-concept for preparing cell-permeable stapled peptide inhibitors of the estrogen receptor/coactivator interaction.

Stafford JL, Dyson G, Levin NK, et al.
Reanalysis of BRCA1/2 negative high risk ovarian cancer patients reveals novel germline risk loci and insights into missing heritability.
PLoS One. 2017; 12(6):e0178450 [PubMed] Free Access to Full Article Related Publications
While up to 25% of ovarian cancer (OVCA) cases are thought to be due to inherited factors, the majority of genetic risk remains unexplained. To address this gap, we sought to identify previously undescribed OVCA risk variants through the whole exome sequencing (WES) and candidate gene analysis of 48 women with ovarian cancer and selected for high risk of genetic inheritance, yet negative for any known pathogenic variants in either BRCA1 or BRCA2. In silico SNP analysis was employed to identify suspect variants followed by validation using Sanger DNA sequencing. We identified five pathogenic variants in our sample, four of which are in two genes featured on current multi-gene panels; (RAD51D, ATM). In addition, we found a pathogenic FANCM variant (R1931*) which has been recently implicated in familial breast cancer risk. Numerous rare and predicted to be damaging variants of unknown significance were detected in genes on current commercial testing panels, most prominently in ATM (n = 6) and PALB2 (n = 5). The BRCA2 variant p.K3326*, resulting in a 93 amino acid truncation, was overrepresented in our sample (odds ratio = 4.95, p = 0.01) and coexisted in the germline of these women with other deleterious variants, suggesting a possible role as a modifier of genetic penetrance. Furthermore, we detected loss of function variants in non-panel genes involved in OVCA relevant pathways; DNA repair and cell cycle control, including CHEK1, TP53I3, REC8, HMMR, RAD52, RAD1, POLK, POLQ, and MCM4. In summary, our study implicates novel risk loci as well as highlights the clinical utility for retesting BRCA1/2 negative OVCA patients by genomic sequencing and analysis of genes in relevant pathways.

Carter JV, Galbraith NJ, Yang D, et al.
Blood-based microRNAs as biomarkers for the diagnosis of colorectal cancer: a systematic review and meta-analysis.
Br J Cancer. 2017; 116(6):762-774 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Colorectal cancer (CRC) is common and associated with significant mortality. Current screening methods for CRC lack patient compliance. microRNAs (miRNAs), identified in body fluids, are negative regulators of gene expression and are dysregulated in many cancers, including CRC. This paper summarises studies identifying blood-based miRNAs dysregulated in CRC compared with healthy controls in an attempt to evaluate their use as a screening tool for the diagnosis of CRC.
METHODS: A search of electronic databases (PubMed and EMBASE) and grey literature was performed between January 2002 and April 2016. Studies reporting plasma or serum miRNAs in the diagnosis of CRC compared with healthy controls were selected. Patient demographics, type of patient sample (serum or plasma), method of miRNA detection, type of normalisation, and the number of significantly dysregulated miRNAs identified were recorded. Statistical evaluation of dysregulated miRNAs using sensitivity, specificity, and area under the curve (AUC) was performed.
RESULTS: Thirty-four studies investigating plasma or serum miRNAs in the diagnosis of CRC were included. A total of 31 miRNAs were found to be either upregulated (n=17) or downregulated (n=14) in CRC cases as compared with controls. Fourteen studies identified panels of ⩾2 dysregulated miRNAs. The highest AUC, 0.943, was identified using a panel of 4 miRNAs with 83.3% sensitivity and 93.1% specificity. Meta-analysis of studies identifying a single dysregulated miRNA in CRC cases compared with controls was performed. Overall sensitivity and specificity of 28 individual miRNAs in the diagnosis of CRC were 76% (95% CI 72%-80%) and 76% (95% CI 72%-80%), respectively, indicating good discriminative ability of miRNAs as biomarkers for CRC. These data did not change with sensitivity analyses.
CONCLUSIONS: Blood-based miRNAs distinguish patients with CRC from healthy controls with high sensitivity and specificity comparable to other common and invasive currently used screening methods for CRC. In future, miRNAs may be used as a relatively non-invasive blood-based marker for detection of CRC.

Simbolo M, Mafficini A, Sikora KO, et al.
Lung neuroendocrine tumours: deep sequencing of the four World Health Organization histotypes reveals chromatin-remodelling genes as major players and a prognostic role for TERT, RB1, MEN1 and KMT2D.
J Pathol. 2017; 241(4):488-500 [PubMed] Free Access to Full Article Related Publications
Next-generation sequencing (NGS) was applied to 148 lung neuroendocrine tumours (LNETs) comprising the four World Health Organization classification categories: 53 typical carcinoid (TCs), 35 atypical carcinoid (ACs), 27 large-cell neuroendocrine carcinomas, and 33 small-cell lung carcinomas. A discovery screen was conducted on 46 samples by the use of whole-exome sequencing and high-coverage targeted sequencing of 418 genes. Eighty-eight recurrently mutated genes from both the discovery screen and current literature were verified in the 46 cases of the discovery screen, and validated on additional 102 LNETs by targeted NGS; their prevalence was then evaluated on the whole series. Thirteen of these 88 genes were also evaluated for copy number alterations (CNAs). Carcinoids and carcinomas shared most of the altered genes but with different prevalence rates. When mutations and copy number changes were combined, MEN1 alterations were almost exclusive to carcinoids, whereas alterations of TP53 and RB1 cell cycle regulation genes and PI3K/AKT/mTOR pathway genes were significantly enriched in carcinomas. Conversely, mutations in chromatin-remodelling genes, including those encoding histone modifiers and members of SWI-SNF complexes, were found at similar rates in carcinoids (45.5%) and carcinomas (55.0%), suggesting a major role in LNET pathogenesis. One AC and one TC showed a hypermutated profile associated with a POLQ damaging mutation. There were fewer CNAs in carcinoids than in carcinomas; however ACs showed a hybrid pattern, whereby gains of TERT, SDHA, RICTOR, PIK3CA, MYCL and SRC were found at rates similar to those in carcinomas, whereas the MEN1 loss rate mirrored that of TCs. Multivariate survival analysis revealed RB1 mutation (p = 0.0005) and TERT copy gain (p = 0.016) as independent predictors of poorer prognosis. MEN1 mutation was associated with poor prognosis in AC (p = 0.0045), whereas KMT2D mutation correlated with longer survival in SCLC (p = 0.0022). In conclusion, molecular profiling may complement histology for better diagnostic definition and prognostic stratification of LNETs. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Wang T, Lu Y, Polk A, et al.
T-cell Receptor Signaling Activates an ITK/NF-κB/GATA-3 axis in T-cell Lymphomas Facilitating Resistance to Chemotherapy.
Clin Cancer Res. 2017; 23(10):2506-2515 [PubMed] Free Access to Full Article Related Publications

Dai CH, Chen P, Li J, et al.
Co-inhibition of pol θ and HR genes efficiently synergize with cisplatin to suppress cisplatin-resistant lung cancer cells survival.
Oncotarget. 2016; 7(40):65157-65170 [PubMed] Free Access to Full Article Related Publications
Cisplatin exert its anticancer effect by creating intrastrand and interstrand DNA cross-links which block DNA replication and is a major drug used to treat lung cancer. However, the main obstacle of the efficacy of treatment is drug resistance. Here, we show that expression of translesion synthesis (TLS) polymerase Q (POLQ) was significantly elevated by exposure of lung cancer cells A549/DR (a cisplatin-resistant A549 cell line) to cisplatin. POLQ expression correlated inversely with homologous recombination (HR) activity. Co-depletion of BRCA2 and POLQ by siRNA markedly increased sensitivity of A549/DR cells to cisplatin, which was accompanied with impairment of double strand breaks (DSBs) repair reflected by prominent cell cycle checkpoint response, increased chromosomal aberrations and persistent colocalization of p-ATM and 53BP1 foci induced by cisplatin. Thus, co-knockdown of POLQ and HR can efficiently synergize with cisplatin to inhibit A549/DR cell survival by inhibiting DNA DSBs repair. Similar results were observed in A549/DR cells co-depleted of BRCA2 and POLQ following BMN673 (a PARP inhibitor) treatment. Importantly, the sensitization effects to cisplatin and BMN673 in A549/DR cells by co-depleting BRCA2 and POLQ was stronger than those by co-depleting BRCA2 and other TLS factors including POLH, REV3, or REV1. Our results indicate that there is a synthetic lethal relationship between pol θ-mediated DNA repair and HR pathways. Pol θ may be considered as a novel target for lung cancer therapy.

Zhao G, Liu L, Peek RM, et al.
Activation of Epidermal Growth Factor Receptor in Macrophages Mediates Feedback Inhibition of M2 Polarization and Gastrointestinal Tumor Cell Growth.
J Biol Chem. 2016; 291(39):20462-72 [PubMed] Free Access to Full Article Related Publications
EGF receptor (EGFR) in tumor cells serves as a tumor promoter. However, information about EGFR activation in macrophages in regulating M2 polarization and tumor development is limited. This study aimed to investigate the effects of EGFR activation in macrophages on M2 polarization and development of gastrointestinal tumors. IL-4, a cytokine to elicit M2 polarization, stimulated release of an EGFR ligand, HB-EGF, and transactivation and down-regulation of EGFR in Raw 264.7 cells and peritoneal macrophages from WT mice. Knockdown of HB-EGF in macrophages inhibited EGFR transactivation by IL-4. IL-4-stimulated STAT6 activation, Arg1 and YM1 gene expression, and HB-EGF production were further enhanced by inhibition of EGFR activity in Raw 264.7 cells using an EGFR kinase inhibitor and in peritoneal macrophages from Egfr(wa5) mice with kinase inactive EGFR and by knockdown of EGFR in peritoneal macrophages from Egfr(fl/fl) LysM-Cre mice with myeloid cell-specific EGFR deletion. Chitin induced a higher level of M2 polarization in peritoneal macrophages in Egfr(fl/fl) LysM-Cre mice than that in Egfr(fl/fl) mice. Accordingly, IL-4-conditioned medium stimulated growth and epithelial-to-mesenchymal transition in gastric epithelial and colonic tumor cells, which were suppressed by that from Raw 264.7 cells with HB-EGF knockdown but promoted by that from Egfr(wa5) and Egfr(fl/fl) LysM-Cre peritoneal macrophages. Clinical assessment revealed that the number of macrophages with EGFR expression became less, indicating decreased inhibitory effects on M2 polarization, in late stage of human gastric cancers. Thus, IL-4-stimulated HB-EGF-dependent transactivation of EGFR in macrophages may mediate inhibitory feedback for M2 polarization and HB-EGF production, thereby inhibiting gastrointestinal tumor growth.

Wood RD, Doublié S
DNA polymerase θ (POLQ), double-strand break repair, and cancer.
DNA Repair (Amst). 2016; 44:22-32 [PubMed] Free Access to Full Article Related Publications
DNA polymerase theta (pol θ) is encoded in the genomes of many eukaryotes, though not in fungi. Pol θ is encoded by the POLQ gene in mammalian cells. The C-terminal third of the protein is a family A DNA polymerase with additional insertion elements relative to prokaryotic homologs. The N-terminal third is a helicase-like domain with DNA-dependent ATPase activity. Pol θ is important in the repair of genomic double-strand breaks (DSBs) from many sources. These include breaks formed by ionizing radiation and topoisomerase inhibitors, breaks arising at stalled DNA replication forks, breaks introduced during diversification steps of the mammalian immune system, and DSB induced by CRISPR-Cas9. Pol θ participates in a route of DSB repair termed "alternative end-joining" (altEJ). AltEJ is independent of the DNA binding Ku protein complex and requires DNA end resection. Pol θ is able to mediate joining of two resected 3' ends harboring DNA sequence microhomology. "Signatures" of Pol θ action during altEJ are the frequent utilization of longer microhomologies, and the insertion of additional sequences at joining sites. The mechanism of end-joining employs the ability of Pol θ to tightly grasp a 3' terminus through unique contacts in the active site, allowing extension from minimally paired primers. Pol θ is involved in controlling the frequency of chromosome translocations and preserves genome integrity by limiting large deletions. It may also play a backup role in DNA base excision repair. POLQ is a member of a cluster of similarly upregulated genes that are strongly correlated with poor clinical outcome for breast cancer, ovarian cancer and other cancer types. Inhibition of pol θ is a compelling approach for combination therapy of radiosensitization.

Dai ZJ, Liu XH, Ma YF, et al.
Association Between Single Nucleotide Polymorphisms in DNA Polymerase Kappa Gene and Breast Cancer Risk in Chinese Han Population: A STROBE-Compliant Observational Study.
Medicine (Baltimore). 2016; 95(2):e2466 [PubMed] Free Access to Full Article Related Publications
DNA polymerases are responsible for ensuring stability of the genome and avoiding genotoxicity caused by a variety of factors during DNA replication. Consequently, these proteins have been associated with an increased cancer risk. DNA polymerase kappa (POLK) is a specialized DNA polymerase involved in translesion DNA synthesis (TLS) that allows DNA synthesis over the damaged DNA. Recently, some studies investigated relationships between POLK polymorphisms and cancer risk, but the role of POLK genetic variants in breast cancer (BC) remains to be defined. In this study, we aimed to evaluate the effects of POLK polymorphisms on BC risk.We used the Sequenom MassARRAY method to genotype 3 single nucleotide polymorphisms (SNPs) in POLK (rs3213801, rs10077427, and rs5744533), in order to determine the genotypes of 560 BC patients and 583 controls. The association of genotypes and BC was assessed by computing the odds ratio (OR) and 95% confidence intervals (95% CIs) from logistic regression analyses.We found a statistically significant difference between patient and control groups in the POLK rs10077427 genotypic groups, excluding the recessive model. A positive correlation was also found between positive progesterone receptor (PR) status, higher Ki67 index, and rs10077427 polymorphism. For rs5744533 polymorphism, the codominant, dominant, and allele models frequencies were significantly higher in BC patients compared to healthy controls. Furthermore, our results indicated that rs5744533 SNP has a protective role in the postmenopausal women. However, we failed to find any associations between rs3213801 polymorphism and susceptibility to BC.Our results indicate that POLK polymorphisms may influence the risk of developing BC, and, because of this, may serve as a prognostic biomarker among Chinese women.

Bostian AC, Maddukuri L, Reed MR, et al.
Kynurenine Signaling Increases DNA Polymerase Kappa Expression and Promotes Genomic Instability in Glioblastoma Cells.
Chem Res Toxicol. 2016; 29(1):101-8 [PubMed] Free Access to Full Article Related Publications
Overexpression of the translesion synthesis polymerase hpol κ in glioblastomas has been linked to poor patient prognosis; however, the mechanism promoting higher expression in these tumors remains unknown. We determined that activation of the aryl hydrocarbon receptor (AhR) pathway in glioblastoma cells leads to increased hpol κ mRNA and protein levels. We blocked nuclear translocation and DNA binding by AhR in glioblastoma cells using a small-molecule and observed decreased hpol κ expression. Pharmacological inhibition of tryptophan-2,3-dioxygenase (TDO), the enzyme largely responsible for activating AhR in glioblastoma, led to a decrease in the endogenous AhR agonist kynurenine and a corresponding decrease in hpol κ protein levels. Importantly, we discovered that inhibiting TDO activity, AhR signaling, or suppressing hpol κ expression with RNA interference led to decreased chromosomal damage in glioblastoma cells. Epistasis assays further supported the idea that TDO activity, activation of AhR signaling, and the resulting overexpression of hpol κ function primarily in the same pathway to increase endogenous DNA damage. These findings indicate that upregulation of hpol κ through glioblastoma-specific TDO activity and activation of AhR signaling likely contributes to the high levels of replication stress and genomic instability observed in these tumors.

Edwards L, Gupta R, Filipp FV
Hypermutation of DPYD Deregulates Pyrimidine Metabolism and Promotes Malignant Progression.
Mol Cancer Res. 2016; 14(2):196-206 [PubMed] Free Access to Full Article Related Publications
UNLABELLED: New strategies are needed to diagnose and target human melanoma. To this end, genomic analyses was performed to assess somatic mutations and gene expression signatures using a large cohort of human skin cutaneous melanoma (SKCM) patients from The Cancer Genome Atlas (TCGA) project to identify critical differences between primary and metastatic tumors. Interestingly, pyrimidine metabolism is one of the major pathways to be significantly enriched and deregulated at the transcriptional level in melanoma progression. In addition, dihydropyrimidine dehydrogenase (DPYD) and other important pyrimidine-related genes: DPYS, AK9, CAD, CANT1, ENTPD1, NME6, NT5C1A, POLE, POLQ, POLR3B, PRIM2, REV3L, and UPP2 are significantly enriched in somatic mutations relative to the background mutation rate. Structural analysis of the DPYD protein dimer reveals a potential hotspot of recurring somatic mutations in the ligand-binding sites as well as the interfaces of protein domains that mediated electron transfer. Somatic mutations of DPYD are associated with upregulation of pyrimidine degradation, nucleotide synthesis, and nucleic acid processing while salvage and nucleotide conversion is downregulated in TCGA SKCM.
IMPLICATIONS: At a systems biology level, somatic mutations of DPYD cause a switch in pyrimidine metabolism and promote gene expression of pyrimidine enzymes toward malignant progression.

Gee HE, Buffa FM, Harris AL, et al.
MicroRNA-Related DNA Repair/Cell-Cycle Genes Independently Associated With Relapse After Radiation Therapy for Early Breast Cancer.
Int J Radiat Oncol Biol Phys. 2015; 93(5):1104-14 [PubMed] Related Publications
PURPOSE: Local recurrence and distant failure after adjuvant radiation therapy for breast cancer remain significant clinical problems, incompletely predicted by conventional clinicopathologic markers. We had previously identified microRNA-139-5p and microRNA-1274a as key regulators of breast cancer radiation response in vitro. The purpose of this study was to investigate standard clinicopathologic markers of local recurrence in a contemporary series and to establish whether putative target genes of microRNAs involved in DNA repair and cell cycle control could better predict radiation therapy response in vivo.
METHODS AND MATERIALS: With institutional ethics board approval, local recurrence was measured in a contemporary, prospectively collected series of 458 patients treated with radiation therapy after breast-conserving surgery. Additionally, independent publicly available mRNA/microRNA microarray expression datasets totaling >1000 early-stage breast cancer patients, treated with adjuvant radiation therapy, with >10 years of follow-up, were analyzed. The expression of putative microRNA target biomarkers--TOP2A, POLQ, RAD54L, SKP2, PLK2, and RAG1--were correlated with standard clinicopathologic variables using 2-sided nonparametric tests, and to local/distant relapse and survival using Kaplan-Meier and Cox regression analysis.
RESULTS: We found a low rate of isolated local recurrence (1.95%) in our modern series, and that few clinicopathologic variables (such as lymphovascular invasion) were significantly predictive. In multiple independent datasets (n>1000), however, high expression of RAD54L, TOP2A, POLQ, and SKP2 significantly correlated with local recurrence, survival, or both in univariate and multivariate analyses (P<.001). Low RAG1 expression significantly correlated with local recurrence (multivariate, P=.008). Additionally, RAD54L, SKP2, and PLK2 may be predictive, being prognostic in radiation therapy-treated patients but not in untreated matched control individuals (n=107; P<.05).
CONCLUSIONS: Biomarkers of DNA repair and cell cycle control can identify patients at high risk of treatment failure in those receiving radiation therapy for early breast cancer in independent cohorts. These should be further investigated prospectively, especially TOP2A and SKP2, for which targeted therapies are available.

Cheng PH, Rao XM, Wechman SL, et al.
Oncolytic adenovirus targeting cyclin E overexpression repressed tumor growth in syngeneic immunocompetent mice.
BMC Cancer. 2015; 15:716 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Clinical trials have indicated that preclinical results obtained with human tumor xenografts in mouse models may overstate the potential of adenovirus (Ad)-mediated oncolytic therapies. We have previously demonstrated that the replication of human Ads depends on cyclin E dysregulation or overexpression in cancer cells. ED-1 cell derived from mouse lung adenocarcinomas triggered by transgenic overexpression of human cyclin E may be applied to investigate the antitumor efficacy of oncolytic Ads.
METHODS: Ad-cycE was used to target cyclin E overexpression in ED-1 cells and repress tumor growth in a syngeneic mouse model for investigation of oncolytic virotherapies.
RESULTS: Murine ED-1 cells were permissive for human Ad replication and Ad-cycE repressed ED-1 tumor growth in immunocompetent FVB mice. ED-1 cells destroyed by oncolytic Ads in tumors were encircled in capsule-like structures, while cells outside the capsules were not infected and survived the treatment.
CONCLUSION: Ad-cycE can target cyclin E overexpression in cancer cells and repress tumor growth in syngeneic mouse models. The capsule structures formed after Ad intratumoral injection may prevent viral particles from spreading to the entire tumor.

Abegglen LM, Caulin AF, Chan A, et al.
Potential Mechanisms for Cancer Resistance in Elephants and Comparative Cellular Response to DNA Damage in Humans.
JAMA. 2015; 314(17):1850-60 [PubMed] Free Access to Full Article Related Publications
IMPORTANCE: Evolutionary medicine may provide insights into human physiology and pathophysiology, including tumor biology.
OBJECTIVE: To identify mechanisms for cancer resistance in elephants and compare cellular response to DNA damage among elephants, healthy human controls, and cancer-prone patients with Li-Fraumeni syndrome (LFS).
DESIGN, SETTING, AND PARTICIPANTS: A comprehensive survey of necropsy data was performed across 36 mammalian species to validate cancer resistance in large and long-lived organisms, including elephants (n = 644). The African and Asian elephant genomes were analyzed for potential mechanisms of cancer resistance. Peripheral blood lymphocytes from elephants, healthy human controls, and patients with LFS were tested in vitro in the laboratory for DNA damage response. The study included African and Asian elephants (n = 8), patients with LFS (n = 10), and age-matched human controls (n = 11). Human samples were collected at the University of Utah between June 2014 and July 2015.
EXPOSURES: Ionizing radiation and doxorubicin.
MAIN OUTCOMES AND MEASURES: Cancer mortality across species was calculated and compared by body size and life span. The elephant genome was investigated for alterations in cancer-related genes. DNA repair and apoptosis were compared in elephant vs human peripheral blood lymphocytes.
RESULTS: Across mammals, cancer mortality did not increase with body size and/or maximum life span (eg, for rock hyrax, 1% [95% CI, 0%-5%]; African wild dog, 8% [95% CI, 0%-16%]; lion, 2% [95% CI, 0%-7%]). Despite their large body size and long life span, elephants remain cancer resistant, with an estimated cancer mortality of 4.81% (95% CI, 3.14%-6.49%), compared with humans, who have 11% to 25% cancer mortality. While humans have 1 copy (2 alleles) of TP53, African elephants have at least 20 copies (40 alleles), including 19 retrogenes (38 alleles) with evidence of transcriptional activity measured by reverse transcription polymerase chain reaction. In response to DNA damage, elephant lymphocytes underwent p53-mediated apoptosis at higher rates than human lymphocytes proportional to TP53 status (ionizing radiation exposure: patients with LFS, 2.71% [95% CI, 1.93%-3.48%] vs human controls, 7.17% [95% CI, 5.91%-8.44%] vs elephants, 14.64% [95% CI, 10.91%-18.37%]; P < .001; doxorubicin exposure: human controls, 8.10% [95% CI, 6.55%-9.66%] vs elephants, 24.77% [95% CI, 23.0%-26.53%]; P < .001).
CONCLUSIONS AND RELEVANCE: Compared with other mammalian species, elephants appeared to have a lower-than-expected rate of cancer, potentially related to multiple copies of TP53. Compared with human cells, elephant cells demonstrated increased apoptotic response following DNA damage. These findings, if replicated, could represent an evolutionary-based approach for understanding mechanisms related to cancer suppression.

Rice J, Roberts H, Rai SN, Galandiuk S
Housekeeping genes for studies of plasma microRNA: A need for more precise standardization.
Surgery. 2015; 158(5):1345-51 [PubMed] Related Publications
INTRODUCTION: Plasma microRNAs (miRNAs) are promising biomarkers for many forms of cancer in humans; however, a fundamental concern is the lack of standardization in current data acquisition and reporting. Part of this problem lies in the use of numerous, different housekeeping genes (HKG) for the acquisition of real-time polymerase chain reaction data. This existing practice of using different HKGs generally is accepted, but reproducibility of data for comparison and validation between different laboratories calls for improvement. The need for data reproducibility standardization is crucial. An ideal plasma HKG (1) should be expressed in all samples, (2) have medium-to-high levels of expression, and (3) have consistently measurable levels of expression.
METHODS: Total RNA was extracted from 200-μL plasma samples via a modified miRNeasy (QIAGEN) extraction technique with yeast carrier. Total RNA purity was assessed with a Nanodrop 2000 spectrophotometer (Thermo Scientific). The cycle threshold (Ct) was fixed at 0.03 for all samples. We investigated 10 potential HKGs based both on reports in the literature and our previous data. The potential HKGs were Let-7a, Let-7d, Let-7g, miR-16, RNU6, RNU48, miR-191, miR-223, miR-484, and miR-520d-5p. Once all samples were run for each potential HKG, the mean Ct and SD was calculated for all sample groups, allowing for comparison among HKGs.
RESULTS: We screened 380 miRNAs by using microfluidic array technology (Applied Biosystems) in a discovery cohort of 20 colorectal cancer (CRC) patients, 10 patients each with breast cancer (BC), lung cancer (LC), pancreatic cancer (PC), 11 patients with colorectal adenoma, and 12 controls. The mean Ct and SD was calculated for RNU6, miR-520d-5p, miR-16, miR-191, miR-223, and miR-484, which were expressed in all samples. Let-7a, Let-7d, Let-7g, and RNU48 were only expressed in 26%, 7%, 10%, and 8% of samples, respectively, and therefore were deemed to be insufficiently reliable HKGs. Only miRNAs with >50% expression were included in this statistical analysis. U6 and miR-520d-5p had the most consistent Ct as well as the least SD. The use of both RNU6 and 520d-5p as HKGs provided reliable results.
CONCLUSION: Among HKGs that were expressed in all samples, we suggest that RNU6 and miR-520d-5p were the best candidates for HKGs for studies of plasma miRNA because of the consistent and high Ct in all samples and a very narrow, reproducible SD.

Yadav S, Mukhopadhyay S, Anbalagan M, Makridakis N
Somatic Mutations in Catalytic Core of POLK Reported in Prostate Cancer Alter Translesion DNA Synthesis.
Hum Mutat. 2015; 36(9):873-80 [PubMed] Free Access to Full Article Related Publications
DNA polymerase kappa is a Y-family polymerase that participates to bypass the damaged DNA known as translesion synthesis (TLS) polymerase. Higher frequency of mutations in DNA polymerase kappa (POLK) recently been reported in prostate cancer. We sequenced entire exons of the POLK gene on genomic DNA from 40 prostate cancers and matched normal samples. We identified that 28% of patients have somatic mutations in the POLK gene of the prostate tumors. Mutations in these prostate cancers have somatic mutation spectra, which are dominated by C-to-T transitions. In the current study, we further investigate the effect of p.E29K, p.G154E, p.F155S, p.E430K, p.L442F, and p.E449K mutations on the biochemical properties of the polymerase in vitro, using TLS assay and nucleotide incorporation fidelity, following site-directed mutagenesis bacterial expression, and purification of the respective polymerase variants. We report that following missense mutations p.E29K, p.G154E, p.F155S, p.E430K, and p.L442F significantly diminished the catalytic efficiencies of POLK with regard to the lesion bypass (AP site). POLK variants show extraordinarily low fidelity by misincorporating T, C, and G as compared to wild-type variants. Taken together, these results suggest that interfering with normal polymerase kappa function by these mutations may be involved in prostate carcinogenesis.

Hong SH, Tilan JU, Galli S, et al.
High neuropeptide Y release associates with Ewing sarcoma bone dissemination - in vivo model of site-specific metastases.
Oncotarget. 2015; 6(9):7151-65 [PubMed] Free Access to Full Article Related Publications
Ewing sarcoma (ES) develops in bones or soft tissues of children and adolescents. The presence of bone metastases is one of the most adverse prognostic factors, yet the mechanisms governing their formation remain unclear. As a transcriptional target of EWS-FLI1, the fusion protein driving ES transformation, neuropeptide Y (NPY) is highly expressed and released from ES tumors. Hypoxia up-regulates NPY and activates its pro-metastatic functions. To test the impact of NPY on ES metastatic pattern, ES cell lines, SK-ES1 and TC71, with high and low peptide release, respectively, were used in an orthotopic xenograft model. ES cells were injected into gastrocnemius muscles of SCID/beige mice, the primary tumors excised, and mice monitored for the presence of metastases. SK-ES1 xenografts resulted in thoracic extra-osseous metastases (67%) and dissemination to bone (50%) and brain (25%), while TC71 tumors metastasized to the lungs (70%). Bone dissemination in SK-ES1 xenografts associated with increased NPY expression in bone metastases and its accumulation in bone invasion areas. The genetic silencing of NPY in SK-ES1 cells reduced bone degradation. Our study supports the role for NPY in ES bone invasion and provides new models for identifying pathways driving ES metastases to specific niches and testing anti-metastatic therapeutics.

Ceccaldi R, Liu JC, Amunugama R, et al.
Homologous-recombination-deficient tumours are dependent on Polθ-mediated repair.
Nature. 2015; 518(7538):258-62 [PubMed] Free Access to Full Article Related Publications
Large-scale genomic studies have shown that half of epithelial ovarian cancers (EOCs) have alterations in genes regulating homologous recombination (HR) repair. Loss of HR accounts for the genomic instability of EOCs and for their cellular hyper-dependence on alternative poly-ADP ribose polymerase (PARP)-mediated DNA repair mechanisms. Previous studies have implicated the DNA polymerase θ (Polθ also known as POLQ, encoded by POLQ) in a pathway required for the repair of DNA double-strand breaks, referred to as the error-prone microhomology-mediated end-joining (MMEJ) pathway. Whether Polθ interacts with canonical DNA repair pathways to prevent genomic instability remains unknown. Here we report an inverse correlation between HR activity and Polθ expression in EOCs. Knockdown of Polθ in HR-proficient cells upregulates HR activity and RAD51 nucleofilament assembly, while knockdown of Polθ in HR-deficient EOCs enhances cell death. Consistent with these results, genetic inactivation of an HR gene (Fancd2) and Polq in mice results in embryonic lethality. Moreover, Polθ contains RAD51 binding motifs and it blocks RAD51-mediated recombination. Our results reveal a synthetic lethal relationship between the HR pathway and Polθ-mediated repair in EOCs, and identify Polθ as a novel druggable target for cancer therapy.

Disclaimer: This site is for educational purposes only; it can not be used in diagnosis or treatment.

Cite this page: Cotterill SJ. POLK, Cancer Genetics Web: http://www.cancer-genetics.org/POLK.htm Accessed:

Creative Commons License
This page in Cancer Genetics Web by Simon Cotterill is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
Note: content of abstracts copyright of respective publishers - seek permission where appropriate.

 [Home]    Page last revised: 01 September, 2019     Cancer Genetics Web, Established 1999